**3. Results**

#### *3.1. TRP Channel Levels in IBD*

The expression of TRP channels in PBMCs from the IBD and control groups are summarized in Figure 1. The observed fold changes in all TRP channel members were very small. However, when compared with mRNA expression levels in PBMCs from healthy controls (TRPV2, 1.54 ± 0.44; TRPV3, 0.15 ± 0.08; TRPV4, 0.95 ± 0.39; TRPM2, 1.54 ± 0.63; TRPC1, 1.73 ± 0.64), those of TRPV2 and TRPC1 were lower in both UC (1.11 ± 0.39 (0.72-fold), *p* < 0.0001 and 1.15 ± 0.65 (0.66-fold), *p* = 0.0002,respectively) and CD (1.18 ± 0.34 (0.77-fold), *p* = 0.0014 and 1.24 ± 0.65 (0.72-fold), *p* = 0.0021, respectively) groups, those of TRPM2 were higher in both UC (2.20 ± 0.76 (1.43-fold), *p* < 0.0001) and CD (2.28 ± 0.86 (1.47-fold), *p* < 0.0001) groups, those of TRPV3 were lower only in the CD group (0.09 ± 0.06 (0.58-fold), *p* = 0.001), and those of TRPV4 were higher only in the CD (1.40 ± 0.72 (1.48-fold), *p* = 0.0067) group.

**Figure 1.** Expression of transient receptor potential (TRP) channels in healthy subjects, patients with ulcerative colitis (UC) and Crohn's disease (CD). Bars represent mean ± SD. N: Number of subjects. Inter-group significance, Bonferroni-corrected Mann–Whitney U test, *p* < 0.01.

Further, TRPC6 mRNA expression was higher in the CD group (1.68 ± 1.41 (1.79-fold), *p* = 0.0008) than in the UC group (0.94 ± 0.55).

In addition, the mRNA expression levels of each TRP channel in PBMCs from healthy controls were variable. We found that TRPV3 had the lowest (0.15-fold relative to GAPDH) and TRPC1 had the highest (1.73-fold relative to GAPDH) expression.

#### *3.2. Relationship between TRP Channel Levels and Disease Activity*

Figure 2 shows the relationship between the expression of each TRP channel member and the clinical disease progression, assessed using PMS for UC patients, and CDAI for CD patients. There was a tendency observed for the mRNA expression of TRPV2 to negatively correlate with disease activity in both UC and CD groups, while that of TRPM4 was negatively correlated with disease activity in only the UC group. However, the significance of these correlations is questionable since the R<sup>2</sup> values were <0.1.

**Figure 2.** Correlation between TRP channel expression and clinical disease progression in patients with ulcerative colitis (UC) and Crohn's disease (CD). Clinical disease progression was assessed using the partial Mayo score (PMS) for patients with UC and the CD activity index (CDAI) for patients with CD. N: Number of patients.

#### *3.3. Correlation between Expression of TRP Channels and Clinical Parameters*

Table 3 summarizes the correlation coefficients and significance values for comparisons between the expression of each TRP channel member and the indicated laboratory parameters. In the UC group, mRNA expression of TRPV2 and TRPV3 negatively correlated with the leukocyte count, while that of TRPV4 and TRPM5 positively correlated with the serum albumin and hemoglobin levels, respectively. In the CD group, the expression of TRPV4 positively correlated with the CRP level.

#### *3.4. Relationship between TRP Channel Expression and Medical Treatment*

We also assessed the relationship between each TRP channel member and medical treatment received by the patient. Since the number of patients in each group was fairly small, no significant association was found between individual TRP channel members and specific medical treatments (Supplementary Figure S1).


**Table 3.** Correlation coefficients and significance of differences between each transient receptor potential (TRP) channel expression and laboratory parameters in patients with ulcerative colitis (UC) or Crohn's disease (CD).

Alb: Albumin; CRP: C-reactive protein; Hb: Hemoglobin; WBC: White blood cell. \* *p* < 0.05, \*\* *p* < 0.005.
